Integration using Cumtrapz backwards instead of forwards

Question

Ramses Young 2021-11-19

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1591209-integration-using-cumtrapz-backwards-instead-of-forwards

评论： Ramses Young 2021-11-20

Hey all, I am trying to create a program that will take distributed point loads from lift generated by a wing and create moment and shear diagrams using numerical integration through cumtrapz

The way I am doing this is by integrating the points and locations which gets me a shear force, but because cumtrapz integrates numerically forward, it technically creates the right graph but backwards from a conventional beam analysis, which creates cuts. Is it possible to make Cumtrapz work backwards? I have attached images of what I want vs what I get for an example

Desired Shear diagram

Obtained Shear Diagram

The obvious solution is just to subtract the maximum value from the graph but this does not encapsulate the essence of what's going on, and also creates a further problem in the bending moment diagram.

Here's the code

L_dist   =[10 9 8 7 6 5 4 3 2 1 0];
locations=[0 1 2 3 4 5 6 7 8 9 10];
shear.z = cumtrapz(locations,(L_dist));
figure('Name','shear - z','NumberTitle','off');
plot(locations, shear.z);